Apparatus and Method for Measuring Level

ABSTRACT

A vessel with a cavity for measuring level is disclosed. The vessel includes a differential pressure sensor having a first port and a second port, a reference tube that connects the first port of the differential pressure sensor to a bottom portion of the cavity, and an impulse tube that connects the second port of the differential pressure sensor to an impulse tube ending. At least a portion of the impulse tube extends through the cavity and ends at a fluid inlet. The fluid inlet is located at a level above the reference tube.

GOVERNMENT INTEREST STATEMENT

This invention was made with government support under DE-FE0028697awarded by the Department of Energy. The government has certain rightsin the invention.

TECHNICAL FIELD

The devices, systems, and methods described herein relate generally tolevel detection. More particularly, the devices, systems, and methodsdescribed herein relate to determining level by differential pressure.

BACKGROUND

Determining level in fluids is required in most industries. Levelinstruments include devices such as floats, ultrasonic transmitters,radar transmitters, nuclear detectors, and differential pressuretransmitters. Often, differential pressure transmitters are external tothe vessel in which the fluid level is being measured. Differentialpressure transmitters measure level by determining the pressure of thefluid in a vessel for at least two levels and using the difference todetermine how much liquid is in the vessel. Measurements where thefluids are at extremes of temperatures can be problematic due totemperature differences between the fluid in the vessel and any fluidsin the differential pressure transmitters.

SUMMARY

In a first aspect, the apparatus includes a vessel with a cavity. Thevessel includes a differential pressure sensor having a first port and asecond port, a reference tube that connects the first port of thedifferential pressure sensor to a bottom portion of the cavity, and animpulse tube that connects the second port of the differential pressuresensor to an impulse tube ending. At least a portion of the impulse tubeextends through the cavity and ends at a fluid inlet. The fluid inlet islocated at a level above the reference tube.

In a second aspect, a method for measuring level includes the step ofpassing a process fluid into a vessel. A portion of the process fluidfills a fluid inlet of an impulse tube of a differential pressuresensor. The differential pressure sensor includes a reference tube. Thereference tube connects the differential pressure sensor to a bottomportion of the vessel. The impulse tube passes from the differentialpressure sensor into the vessel and ends at the fluid inlet. Thepressure difference created by the portion of the process fluid thatpasses into the fluid inlet compared to a pressure of the reference tubeis measured.

The level may be between the reference tube and a full height of thevessel.

The impulse tube ending may be a fluid inlet. The vessel may include avessel inlet. The vessel inlet may be situated such that at least aportion of a process fluid entering the vessel may pass into the fluidinlet of the impulse tube, filling the impulse tube with the processfluid.

The differential pressure sensor may detect a pressure difference whenthe process fluid is added to the fluid inlet. The pressure differencemay indicate a level of the process fluid in the vessel.

The vessel may include a retractable cover covering the fluid inlet. Theretractable cover may have an open state and a closed state. Theretractable cover may cover the fluid inlet in the closed state and mayallow the process fluid to pass into the fluid inlet in the open state.

The process fluid may be a cryogenic fluid, a supercritical fluid, or acombination thereof.

The fluid inlet may be a funnel.

The impulse tube may include a hinged area, allowing the impulse tube tobe moved such that a process fluid entering the vessel does not passinto the fluid inlet. The impulse tube ending may be closed and theimpulse tube may be filled with a reference fluid of the same density asa process fluid in the vessel.

The connection of the reference tube to the vessel may be a diaphragmand the reference tube may be filled with a reference fluid of a samedensity as a process fluid in the vessel.

The vessel may include one or more temperature sensors attached to theimpulse tube, the reference tube, or a combination thereof.

The differential pressure sensor may be at least partially enclosedwithin the vessel.

The differential pressure sensor may include a wireless communicationapparatus.

Further aspects and embodiments are provided in the foregoing drawings,detailed description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are provided to illustrate certain embodimentsdescribed herein. The drawings are merely illustrative and are notintended to limit the scope of claimed inventions and are not intendedto show every potential feature or embodiment of the claimed inventions.The drawings are not necessarily drawn to scale; in some instances,certain elements of the drawing may be enlarged with respect to otherelements of the drawing for purposes of illustration.

FIG. 1 is a cross-sectional elevation view of a vessel with adifferential pressure transmitter.

FIG. 2 is a cross-sectional elevation view of a vessel with adifferential pressure transmitter.

FIG. 3 is an isometric front top view of an impulse tube with a cap.

FIG. 4 is an isometric front elevation view of a vessel with adifferential pressure transmitter, with non-opaque vessel walls.

FIG. 5 is a cross-sectional elevation view of a vessel with adifferential pressure transmitter.

FIG. 6 is a method for measuring level in a vessel.

DETAILED DESCRIPTION

The following description recites various aspects and embodiments of theinventions disclosed herein. No particular embodiment is intended todefine the scope of the invention. Rather, the embodiments providenon-limiting examples of various compositions, and methods that areincluded within the scope of the claimed inventions. The description isto be read from the perspective of one of ordinary skill in the art.Therefore, information that is well known to the ordinarily skilledartisan is not necessarily included.

Definitions

The following terms and phrases have the meanings indicated below,unless otherwise provided herein. This disclosure may employ other termsand phrases not expressly defined herein. Such other terms and phrasesshall have the meanings that they would possess within the context ofthis disclosure to those of ordinary skill in the art. In someinstances, a term or phrase may be defined in the singular or plural. Insuch instances, it is understood that any term in the singular mayinclude its plural counterpart and vice versa, unless expresslyindicated to the contrary.

As used herein, the singular forms “a,” “an,” and “the” include pluralreferents unless the context clearly dictates otherwise. For example,reference to “a substituent” encompasses a single substituent as well astwo or more substituents, and the like.

As used herein, “for example,” “for instance,” “such as,” or “including”are meant to introduce examples that further clarify more generalsubject matter. Unless otherwise expressly indicated, such examples areprovided only as an aid for understanding embodiments illustrated in thepresent disclosure and are not meant to be limiting in any fashion. Nordo these phrases indicate any kind of preference for the disclosedembodiment.

As used herein, “transmitter” is meant to refer to transducers,instruments, sensors, measurement devices, or similar devices used formeasuring level.

As used herein, “tube” is meant to refer to pipes and hoses.

As used herein, “cryogenic” is intended to refer to temperatures belowabout −58° F. (−50° C.).

As used herein, “process fluid” is intended to refer to any of a varietyof fluids used in a processing facility. This may be a pure (singlecompound) liquid, a mixed (multi-component) liquid, a slurry (a liquidwith solids entrained), a liquid with entrained gas bubbles, a liquidwith dissolved components, or a mixture of liquids.

Measuring level, especially in cases of cryogenic liquids, can becumbersome if the cryogenic conditions cause deposition oninstrumentation at the interface of the walls of the containing vessel.A traditional differential pressure transmitter includes two ports thatconnect at two different locations on the exterior wall of a vessel.However, this means that the temperature of the fluid in the top(impulse) port, connected by an impulse tube, is at a differenttemperature than the fluid inside the vessel. This temperaturedifference can cause deviations in accuracy. This can be especiallydetrimental when the fluid density varies significantly withtemperature. In the present invention, this is overcome by having theend of the impulse tube inside of the vessel such that the temperatureof the fluid in the impulse tube remains substantially the same as thetemperature of the fluid in the vessel. In a preferred embodiment,“substantially” the same temperature refers to temperatures within 10°C. of each other. In a more preferred embodiment, this refers totemperatures within 2° C. of each other.

The present invention is also especially useful when the fluid rainsdown into the vessel, keeping the fluid isothermal, and when it rainsdown in a way that keeps the impulse tube consistently full, maintaininga consistent static pressure in the impulse tube.

Now referring to FIG. 1, FIG. 1 is a cross-sectional elevation view 100of a vessel with a differential pressure transmitter that may be used inthe devices, methods, and systems disclosed herein. Vessel 102 includesa cavity 120, an inlet pipe 104, a differential pressure transmitter(DPT) 106, a reference tube inlet port 112, and an overflow outlet 140.DPT 106 includes an impulse port 118, a reference port 116, an impulsetube 108, an impulse tube ending funnel 114, and a reference tube 110.The fluid level 126 is below the maximum measurable level 122 at the topof the impulse tube ending funnel 114. The vessel maximum fill level 124is at the overflow outlet 140.

A process fluid 150 is passed into vessel 102 through inlet pipe 104.Impulse tube 108 is filled and the process fluid 150 overflows and fillsvessel 102. The pressure difference between the reference tube 110 andthe impulse tube 108 determines the fluid level 126.

FIG. 2 is a cross-sectional elevation view 200 of a vessel with adifferential pressure transmitter that may be used in the devices,methods, and systems disclosed herein. Vessel 202 includes a cavity 220,an inlet pipe 204, a differential pressure transmitter (DPT) 206, areference tube inlet 212, and an overflow outlet 240. DPT 206, entirelyinside the cavity, includes an impulse port 218, a reference port 216,an impulse tube 208, an impulse tube ending 214, and a reference tube210. The fluid level 226 is below the maximum measurable level 222 atthe top of the impulse tube ending 214. The maximum level 224 is at thetop of vessel 202.

A process fluid 250 is passed into vessel 202 through inlet pipe 204.Impulse tube 208 is filled and the process fluid 250 overflows and fillsvessel 202. The pressure difference between the reference tube 210 andthe impulse tube 208 determines the fluid level 226. DPT 206 transmitsdata wirelessly 228 to a receiver.

FIG. 3 is an isometric front top view 300 of an impulse tube, as in FIG.1, with a cap. The impulse tube 108 ends in impulse tube ending funnel114. A cap 330 with a hinge 332 is mounted on the impulse tube endingfunnel 114. The hinge 332 may be actuated to open or close cap 330. Theactuator is not shown for clarity. By closing cap 330, fluid 150 isdiverted from entering the impulse tube 108. By closing cap 330 afterthe impulse tube 108 is filled, the maximum measurable height becomesthe vessel maximum fill level 124. For this maximum measurable height,the cap 330 and the funnel 114 need to seal so no fluid 150 is incommunication between the impulse tube 108 and the cavity 120.

FIG. 4 is an isometric front elevation view 400 of a vessel with adifferential pressure transmitter, with non-opaque vessel walls, thatmay be used in the devices, methods, and systems disclosed herein.Vessel 402 includes a cavity 420, an inlet pipe 404, a differentialpressure transmitter (DPT) 406, a reference tube inlet port 412, and anoverflow outlet 440. DPT 406 includes an impulse port 418, a referenceport 416, an impulse tube 408, and a reference tube 410. The fluid level426 is below the maximum measurable level 422 at the top of the impulsetube ending funnel 414. The vessel maximum fill level 424 is at theoverflow outlet 440. The impulse tube 408 has a hinged point 434 thatmoves the end of the impulse tube 408 into the path of fluid 450 andback out.

A process fluid 450 is passed into vessel 402 through inlet pipe 404.Impulse tube 408 is filled and the process fluid 450 overflows and fillsvessel 402. At that point, the hinged point actuates and moves theimpulse tube ending out of the path of fluid 450. The pressuredifference between the reference tube 410 and the impulse tube 408determines the fluid level 426.

FIG. 5 is a cross-sectional elevation view 500 of a vessel with adifferential pressure transmitter that may be used in the devices,methods, and systems disclosed herein. Vessel 502 includes a cavity 520,an inlet pipe 504, a differential pressure transmitter (DPT) 506A and B,a reference tube inlet port 512, and an overflow outlet 540. DPT 506Bincludes an impulse port 518, an impulse tube 508, and a temperaturetransmitter 539. DPT 506A includes a reference port 516, a referencetube 510, a temperature transmitter 538, and a diaphragm 536. The fluidlevel 526 is below the maximum measurable level 522 at the top of theimpulse tube ending. The vessel maximum desired fill level 524 is belowthe inlet pipe 504.

A process fluid 550 is passed into vessel 502 through inlet pipe 504.Impulse tube 508 is filled and the process fluid 550 overflows and fillsvessel 502. The pressure difference between the reference tube 510 andthe impulse tube 508 determines the fluid level 526. DPT 506A and Bcommunicate wirelessly 526 to each other, to temperature transmitters538 and 539, and to a receiver.

FIG. 6 is a method 600 for measuring level in a vessel that may be usedin the devices, methods, and systems disclosed herein. At 601, a fluidis passed into a vessel. At 602, an impulse tube of a differentialpressure transmitter (DPT) is filled with a portion of the fluid. At603, a reference of the DPT connects to a bottom portion of the vessel.At 604, the impulse tube passes from the DPT into the vessel and ends ata fluid inlet. At 605, the pressure difference created by the portion ofthe process fluid that passes into the fluid inlet compared to thepressure of the reference tube is measured.

In one embodiment, the impulse tube ending may have a retractable cover.The retractable cover may have an open state and a closed state. Theretractable cover may cover the fluid inlet in the closed state and mayallow the process fluid to pass into the fluid inlet in the open state.

In some embodiments, the process fluid may be a cryogenic fluid, asupercritical fluid, or a combination thereof.

In some embodiments, the impulse tube may be filled with a referencefluid of the same density as a process fluid in the vessel.

In some embodiments, the reference tube to the vessel may be connectedwith a diaphragm and the reference tube may be filled with a referencefluid of a same density as a process fluid in the vessel.

All patents and published patent applications referred to herein areincorporated herein by reference. The invention has been described withreference to various specific and preferred embodiments and techniques.Nevertheless, it understood that many variations and modifications maybe made while remaining within the spirit and scope of the invention.

What is claimed is:
 1. An apparatus, comprising: a vessel comprising acavity; a differential pressure sensor having a first port and a secondport; a reference tube that connects the first port of the differentialpressure sensor to a bottom portion of the cavity; an impulse tube thatconnects the second port of the differential pressure sensor to animpulse tube ending; wherein at least a portion of the impulse tubeextends through the cavity and ends at a fluid inlet; and wherein thefluid inlet is located at a level above the reference tube.
 2. Theapparatus of claim 5, wherein the level is between the reference tubeand a full height of the vessel.
 3. The apparatus of claim 2, whereinthe impulse tube ending comprises a fluid inlet, wherein the vesselincludes a vessel inlet, the vessel inlet situated such that at least aportion of a process fluid entering the vessel passes into the fluidinlet of the impulse tube, filling the impulse tube with the processfluid.
 4. The apparatus of claim 3, wherein the differential pressuresensor detects a pressure difference when the process fluid is added tothe fluid inlet and wherein the pressure difference indicates a level ofthe process fluid in the vessel.
 5. The apparatus of claim 3, furthercomprising a retractable cover, the retractable cover having an openstate and a closed state, wherein the retractable cover covers the fluidinlet in the closed state and the retractable cover allows the processfluid to pass into the fluid inlet in the open state.
 6. The apparatusof claim 5, wherein the process fluid comprises a cryogenic fluid, asupercritical fluid, or a combination thereof.
 7. The apparatus of claim5, wherein the fluid inlet comprises a funnel.
 8. The apparatus of claim2, wherein the impulse tube comprises a hinged area allowing the impulsetube to be moved such that a process fluid entering the vessel does notpass into the fluid inlet.
 9. The apparatus of claim 5, wherein theimpulse tube ending is closed and the impulse tube is filled with areference fluid of the same density as a process fluid in the vessel.10. The apparatus of claim 5, wherein the connection of the referencetube to the vessel comprises a diaphragm and the reference tube isfilled with a reference fluid of a same density as a process fluid inthe vessel.
 11. The apparatus of claim 5, further comprising one or moretemperature sensors, the one or more temperature sensors attached to theimpulse tube, the reference tube, or a combination thereof.
 12. Theapparatus of claim 5, wherein the differential pressure sensor is atleast partially enclosed within the vessel.
 13. The apparatus of claim5, wherein the differential pressure sensor further comprises a wirelesscommunication apparatus.
 14. A method for measuring level comprising:passing a process fluid into a vessel, a portion of the process fluidfilling a fluid inlet of an impulse tube of a differential pressuresensor, wherein the differential pressure sensor further comprises areference tube, the reference tube connecting the differential pressuresensor to a bottom portion of the vessel and the impulse tube passingfrom the differential pressure sensor into the vessel and ending at thefluid inlet; and measuring the pressure difference created by theportion of the process fluid that passes into the fluid inlet comparedto a pressure of the reference tube.
 15. The method of claim 14, whereinthe process fluid to be contained within the vessel comprises acryogenic fluid, a supercritical fluid, or a combination thereof. 16.The method of claim 14, wherein the fluid inlet comprises a funnel. 17.The method of claim 14, wherein the connection of the reference tube tothe vessel comprises a diaphragm and the reference tube is filled with areference liquid of a same density as a fluid in the vessel.
 18. Themethod of claim 14, wherein the impulse tube and reference tube compriseone or more temperature sensors.
 19. The method of claim 14, wherein thedifferential pressure sensor is at least partially enclosed within thevessel.
 20. The method of claim 14, wherein the differential pressuresensor further comprises a wireless communication method.